I have been moving a fair amount of the VS-640's and FINALLY got one on my showroom floor to play around with it. Overall I do like the result of the Metallic Inks. Of the ones we sold, only two were setup to use the Metallic and White. It seems the biggest draw to this in my area is the DUAL CMYK setup, the 64" Print & Cut and the Price.
Those who are using the Metallic have a definite need for it. Especially for retail. It looks pretty sharp on apparel as well. If you have a pretty sharp sense of design and a great eye for detail, you're creativity can really bring in the bucks. However, with the speed and time it takes, I don't think you're going to see to many people shoot for Metallic printing on vehicle wraps LOL
If it's speed you are looking for with the Metallic, I'd go with the XC-540MT. The VS-640 has definitely sparked a LOT of interest as from what I hear from Roland, there are a LOT of units on backorder until at least June.
Again, many people who are interested in this Metallic & White printing are not even based in the Sign Industry so it would be interesting to see what direction this application performs best in.